This is a resubmission of proposal originally submitted for an NHLBI announcement (KW0715040). Sleep apnea is characterized by repetitive cessation of respiration during sleep, with consequent decreases in blood oxygen saturation, repetitive arousals, daytime somnolence, and complex cardiorespiratory disturbances. There is growing recognition that sleep apnea is a frequent cause of hypertension, cardiorespiratory failure premature death. We have shown that 24% of elderly have at least 5 apneas per hour of sleep, but the prevalence of sleep apnea among American adults under age 65 is unknown. We now propose 1) to determine the prevalence of sleep apnea among both sexes age 40 to 64; 2) to examine the longitudinal course of sleep apnea; and, 3) to examine associations of apneas, oxygen desaturations, snoring, high blood pressure, and other biomedical correlates. A structured random sample will be selected by random digit telephone dialing. Subjects will be studied in their homes. Some will followed yearly during the project. Each volunteer will give a brief sleep history and medical review, including blood pressure measurement, the National Interview Survey, And Quality of Well-being Scale. Blood oxygen saturation, pulse rate, snoring, and sleep duration will be recorded for 3 nights. State-of-the-art computerized pulse oximeters and microprocessor- based activity/light monitors will be used. Subjects found to have the most severe sleep respiratory disturbances will undergo laboratory polysomnograms to add descriptive data and to validate the survey methodology. The prevalence of respiratory disturbances in sleep will be analyzed as a function of age and sex. Associations with several aspects of morbidity will be determined. The longitudinal course of respiratory disturbances in sleep will be examined.